1. Technical Field of the Invention
The present invention relates to an antenna device and a method of manufacturing the same. More specifically, the present invention relates to an antenna device suitable for a reflective antenna receiving wideband frequencies and a method of manufacturing the same.
2. Description of the Related Art
As examples of methods of receiving a plurality of radio waves with different frequency bands transmitted from broadcasting satellites and communication satellites by using a single antenna device, the two following methods are disclosed.
A first method is a method in which a plurality of receivers are provided for one reflector (see Japanese Unexamined Utility Model Registration Application Publication No. 5-57912). In this method, a parabolic antenna is provided with a plurality of receivers for one parabolic reflector, because radio waves that are not parallel to the central axis of a parabolic reflector converge on different points from the focal point of the parabolic reflector. This makes it possible to receive broadcasting radio waves and communication radio waves whose angles are different from each other with a single parabolic antenna.
A second method is a method in which a plurality of parabolic antennas are disposed on the external surface of a spherical structure to form an antenna device. Each parabolic antenna includes a parabolic reflector and a receiver. Each parabolic antenna receives a particular radio wave (see Japanese Unexamined Utility Model Registration Application Publication No. 6-38321). In this method, substantially all of the spherical structure can receive radio waves. Therefore, there is almost no need to consider directional characteristics. This makes it possible and easy to receive a plurality of radio waves whose frequency bands are different from each other from a plurality of communication satellites.
According to the above known methods of receiving radio waves, a plurality of receivers are provided for one parabolic reflector to form a parabolic antenna, or an antenna device is formed by using a plurality of parabolic antennas, in order to receive a plurality of radio waves whose frequency bands are different from each other. Therefore, the methods have problems in which the number of parts composing the antenna device is large and the manufacturing cost is expensive.
An object of the present invention is to provide an antenna device that can receive a plurality of radio waves, with a small number of parts and at low cost, and to provide a method of manufacturing the same.